The processing of reactive polymer materials has been widely used in industry for many years and for many application sectors. Among the materials are by way of example epoxy resins, polyurethanes, and silicones. A difference from the processing of thermoplastic materials is that reactive polymer materials allow the shaping process to be combined with chemical crosslinking. This gives heat-resistant moldings (thermosets), a result not achievable with purely thermoplastic materials.
The reactive polymer materials are often processed in molds or else by casting in situ. Examples here are the production of automobile seats (molded foam process) or the casting of epoxy resins around electronic components.
Within the last 20 years, a technique which is also known as FIPFG (formed in place foam gasket) has become established for the sealing of housing components, lamps, or packaging lids. Certain variants of reactive polymer materials are used here, and are applied directly on the respective component in the region of the seal to be produced. They then cure at their location of use and also exhibit a foaming effect. This typically gives a strand-shaped foam structure, providing a sealing bead produced in situ. Typical materials for this are polyurethanes and silicones, which in most cases are produced in the form of 2-component systems. In these processes, a mixture of the two components is applied with the aid of a suitable discharge nozzle, with control of the amount discharged and with control of discharge velocity, onto the component that requires sealing. In most cases this takes place without shaping, i.e. the trajectory of the seal or the height of the seal is not determined by subsequent application of any counterpart, but instead results from free foaming. Examples of other products produced alongside seals in a similar manner are sheet-like layers on components via application of foaming polymer material with the aid of suitable applicator nozzles which move across the component region that requires lamination—an example of a component being an engine hood—and thus apply the polymer material to the area that requires coating.
In contrast to foaming processes that involve shaping and in which the reaction/hardening of the reactive polymer-material system can be accelerated by appropriate adjustment of temperature, the only way of achieving acceleration of the reaction and hardening in the frequently occurring case described where the reactive polymer material is applied without shaping for the lamination of a component or for the application of a sealing strand is to incur major costs, in that the component is, for example, heated in an oven or is treated with microwaves. 2-component polyurethane (PU) foam systems, single-component PU foam systems, single-component silicone foam systems, and especially 2-component silicone foam systems often exhibit relatively slow completion of reaction after they have been applied on industrial components. This requires that in particular 2-component silicone foam systems are almost always post-treated with the aid of an oven after application in order firstly to render the surface of the resultant sealing foam tack-free and secondly to produce the long-term service properties (resilience) which would not develop fully without heat treatment.
However, post-treatment methods of this type are naturally subject to limitations caused by the size of the component, and when a component is transferred into a thermal oven or microwave oven extreme care is always required to avoid damage to the freshly applied polymer material that is still soft or liquid.
Although the known process, and the apparatuses and materials used therein, can produce seals and layers in reproducible quality without post-treatment in an oven or microwave equipment, a possible consequence of the nature of the polymer material used here is that the time required by the material applied to complete its reaction is relatively long, with the frequently disadvantageous consequence that, after the sealing material or lamination material has been applied, the components first have to be stored for some time before they are passed onwards for appropriate use, for example are capable of installation into an automobile. In the case of some materials, the desired product properties cannot be achieved to the desired extent without thermal post-treatment in an oven as explained. Care has to be taken during storage that the polymer material applied is not subject to impression or to any other type of damage as a consequence of which the seal or layer would not be serviceable or at least would not be free from defects.